Human hair is comprised of keratin ("hair keratin"), a tough fibrous protein having a high sulfur content. Hair keratin is routinely exposed to a variety of activities that compromise its structure. For example, simple grooming and styling results in loss of cuticle scale, subjecting the hair's inner cortex to further damage and eventually leading to hair breakage. Shampooing causes frictional damage to cuticle scale and extracts hair protein. Ultraviolet light from the sun reduces the hair's mechanical strength and causes fading of natural and applied hair color. Exposure to chlorinated water in swimming pools causes oxidation of hair keratin, leading to increased protein loss during combing and brushing.
These practices are less damaging to hair than direct exposure to the reactive chemicals commonly used by hair stylists, such as permanent wave agents, hair colors, bleaches, straighteners, peroxides, thio solutions, sodium hydroxide and the like. However, the cumulative effects of daily cleansing, grooming, and ultraviolet light are far greater than the damage associated with the above-mentioned chemicals. However, if hair has been chemically treated, then daily grooming, shampooing and sun exposure has an even greater potential for causing extensive damage.
In view of the above, there is a need for a novel class of hair treatment compositions which provide not only beautifying effects to damaged and non-damaged hair, but also provide superior protection from the various activities mentioned above that compromise hair structure.